The present invention relates to the art of diagnostic imaging. It finds particular application in conjunction with nuclear or gamma cameras and will be described with particular reference thereto. It is to be appreciated, however, that the present invention will also find application in other non-invasive investigation techniques and imaging systems such as single photon planar imaging, whole body nuclear scans, positron emission tomography (PET) and other diagnostic modes.
Positron emission tomography (PET) scanners are known as coincidence imaging devices. In planar coincidence imaging, two radiation detectors oppose each other with a subject disposed between the detectors. Typically, one or more radiopharmaceuticals or radioisotopes capable of generating positron emission radiation are injected into the subject. The radioisotope preferably travels to an organ of interest whose image is to be produced. The detectors scan the subject along a longitudinal axis without rotation producing a data set with incomplete angular sampling, otherwise known as limited angle tomography. Radiation events are detected on each detector and a coincidence circuitry compares and temporally matches the events on each detector. Events on one detector which have a coincident event on the other detector are treated as valid data and may be used in image reconstruction.
Typically, the detector includes a scintillation crystal that is viewed by an array of photomultiplier tubes. The relative outputs of the photomultiplier tubes are processed and corrected, as is conventional in the art, to generate an output signal indicative of (1) a position coordinate on the detector head at which each radiation event is received, and (2) an energy of each event. The energy is used to differentiate between various types of radiation such as multiple emission radiation sources and to eliminate noise, or stray and secondary emission radiation. A two-dimensional image representation is defined by the number of coincidence radiation events or counts received at each coordinate. However during a scan, only a fraction of the events detected are coincidence events. As such, scan times are increased in an effort to obtain a sufficient data sampling for image reconstruction which poses additional inconveniences to the subject and an increase in scanning costs from reduced patient throughput.
The present invention provides a new and improved diagnostic imaging system and method which provides diagnostic information in addition to coincidence events which overcomes the above-referenced problems and others.